Energy consumption due to desktop personal computers (PCs) in the United States alone was around 16 TWh per year in the early part of the millennium and is steadily growing. Energy production is both expensive in terms of monetary costs and the cost of the number of adverse effects on the environment. This makes conservation of energy a popular topic of discussion.
On average, an idle PC consumes around 50 Watts of power when running and just 2 Watts of power when switched off or in a lower power consumption state, known as a “sleep” state. Even though a computer provides these low power states, users in enterprises tend to keep their computers switched on when they are not in use. A significant percentage of computers have their aggressive power management policies disabled by the user. This is in part because users want to work remotely either from home or on their commute and want round-the-clock access to their data on these machines.
Modern commodity network cards have the “Wake-On-LAN” feature enabled. This feature enables waking up of machines by means of a network packet with a machine identifier termed as a “magic packet”. However, this feature works only when a “magic packet” is sent from within the same subnet as the machine that is to be awakened. With this feature, any kind of wakeup within an enterprise network would then require a dedicated machine on every subnet that broadcasts these packets.
One problem, however, with this technique is that it often does not scale and the dedicated proxy becomes a central point of failure. If inter-subnet broadcast of “magic packets” are a requirement then the router configuration needs to be changed to allow these packets to traverse subnets. This is not recommended by enterprise information technology (IT) security personnel as they pose significant security risks.